Several different methods exist for propelling watercraft. Some watercraft are powered by what is known as a jet propulsion system which is driven by an engine of the watercraft. The jet propulsion system typically consists of a jet pump which pressurizes water from the body of water and expels it through a venturi as a jet rearwardly of the watercraft to create thrust. Usually, a steering nozzle is pivotally mounted rearwardly of the venturi. The steering nozzle is operatively connected to a steering assembly of the watercraft which causes it to turn left or right to redirect the jet of water and thereby steer the watercraft.
The jet propulsion system is usually disposed at least in part within a tunnel formed in the rear portion of the hull. The tunnel has front, left, right and top walls formed by the hull and is open at the bottom and at the transom. The front of a jet pump of the jet propulsion system is rigidly mounted to the front wall of the tunnel. The bottom of the tunnel is at least partially closed by a ride plate. The ride plate creates a surface on which the watercraft rides or planes at high speeds.
The jet pump includes a rotor that rotates at high speeds when the watercraft is in operation, thereby creating torsional and axial vibrations, as well as noise. These vibrations are transmitted through the hull to the hands and feet of the riders, and can cause discomfort or reduce the enjoyment of operating the watercraft.
In addition, the front wall of the tunnel must be of a sturdy construction to withstand the vibrations, and may have to be constructed separately from the rest of the hull. The ride plate, which is also situated at the rear of the watercraft, must also be of a sturdy construction, because it is designed to support at least a portion of the weight of the watercraft during operation. The multiplicity of separately-constructed sturdy and heavy components that must be individually assembled to the watercraft results in increased weight and manufacturing cost.
Therefore, there is a need for a watercraft and a jet propulsion system for a watercraft which reduces the amount of vibrations transmitted from the jet propulsion system to the riders and to the hull and the deck.